Spiralift: The Ultimate Telescoping Linear Actuator

November 7, 2010 by Travis Deyle

After many years of searching for the perfect telescoping linear actuator, I would like to share my discovery of the I-Lock Spiralift 75 (ILS75) prototype by Paco Spiralift. The ILS75 has a compact form factor (10x15x15 cm) that can telescope out to 1.6 meters while lifting a 175kg load (350+ lbs). It relies on a system of interlocking horizontal and vertical metal bands that "unroll" to lift a load, a process best illustrated in the videos embedded below. The ILS75 is just one Spiralift offering; others range all the way up to a goliath version (Spiralift ND18) that can lift an 11,000 kg load 12 meters
(25,000 lbs to 40 ft). To date, Spiralift mechanisms have been applied to theater stage-lift systems and automotive lifts. At Hizook, we believe robotics is a compelling application, especially as a robot's vertical spine (eg. on EL-E, Cody, and PR2) -- increasing the robot's effective workspace to include floor and tables, and also for compact and easy transportation. As such, we're working with Paco Spiralift to gauge roboticsts' interest and vet the technical specs of the ILS75 -- tell us what you think in the comments.

The Spiralift Mechanism:

Before we look at the ILS75 in particular, let's look at how the Spiralift mechanism actually works. It is (apparently) referred to as a helical band actuator, and was awarded a US patent (4875660) in 1989. Here is how it works:

I-Lock Spiralift 75 (ILS75)

The new Spiralift prototype (ILS75) is what caught my interest. From Paco Spiralift's ILS75 webpage:

The I-Lock 75 principle of operation is quite simple: two stainless steel bands engage as they rotate to form a remarkably strong lift column resulting in a rigid structure. Its self contained electric motor provides pushing or pulling action with infinite adjustability. The new 100x150x150 mm model, shown here, has travel of 1600 mm and a load capacity of 175 kg. (see product specifications sheet of I-Lock 75) Since higher travel and higher capacity are possible, it is perfectly adapted to a whole new range of applications.

More details are available in the datasheet. We have also been informed of one important caveat: these units are limited to around 25,000 cycles (presumably due to metal fatigue?). Obviously, by now you're now wondering about price. Initial inquiries suggest a MSRP of $1,000 per unit in small volumes, and potentially as low as $400 in volume -- though these are subject to change as development continues, and it wouldn't surprise me if the prices end up higher due to obvious value propositions. For example, these prices are in-line with traditional linear actuators (eg. Festo) and are an order of magnitude lower than competing telescoping linear actuators (eg. Zippermast).

Does this type of actuator interest you? Let us know your thoughts in the comments or via contact page so that we can communicate them to Paco Spiralift. I'll go ahead and kick off the conversation:

I would like know the maximum torque ratings at the apex under full extension.

For our lab's research robots, 25k cycles should be fine over the robot's ~5-7 year lifetime.

Telescoping would vastly simplify relocating our robots, and the price is commensurate with actuators we already purchase.

Significance

A number of prominent mobile manipulating robots (eg. EL-E, Cody, and PR2) incorporate a vertical
linear actuator (a "spine"), increasing their effective workspace to
encompass floors, tables, and shelves.
Unfortunately, lead- and ball-screw mechanisms are usually employed, and they have a fixed height. This dictates a "tall" robot that causes major relocation headaches -- you either ship the robot in a moving truck or stuff a 6-foot-tall robot into the back of a car. [In this regard, I speak from
experience: it's a pain! I have transported EL-E to and from my home in the
backseat of my Honda Civic!] If the robot could shrink for easy
transportation, moving research out of the lab
and into homes becomes a less ungainly proposition.

I'm sure there are probably numerous applications for a low-cost plastic Spiralift too. I'm curious to learn about the feasibility of such a device (fatigue problems?), but I'll leave that discussion for another day...

Comments

I have some familiarity with the earlier versions of the spiralift. Watching them reminds me of the Bugs Bunny cartoon where he and Elmer Fud are on barber chairs, and jack them up into the sky.

My exposure to the device was before the interlocking version was available. When those versions failed, they did so quite catastrophically. One actuator failure might take out neighboring actuators. This new version looks quite intriguing, and should prevent some of the prior failure modes.

I would tend to be concerned that the fit tolerance for each of those interlocking loop must be added to determine the actual looseness of the system. They may maintain their integrety, but the entire system may be prone to wiggling about.

I didn't even realize they made a previous version without interlocking, and I'm not sure how that would work... The horizontal interlocks seem pretty instrumental to this design, mainly for keeping the vertical bands rigidly attached under load. Now, Zippermast makes a system that does not have interlocking horizontal bands, and its load bearing capacity seems to be much less as a result.

As for tolerance in the interlocks... My understanding is that it can be quite tight. Presumably the CAM rollers are removing all the axial (vertical) load as new vertical bands are aligned, making the insertion relatively low friction and allowing much tighter tolerances. However, you do bring up a good point: how "loose" is the system. One figure of merit might be to measure the deflection at the top under various torques (transverse forces), sort of like a spring. This would also be a good measurement to have.

Heh, I can imagine how a failure with a 175kg mass lifted 1.6 meters could be "catastrophic" -- that's true of just about any system. What did your failures look like (pictures?), what was the time-to-failure (cycles / load?), and were there any warning indicators? Also, I presume you were using them for stage systems with more than one actuator...? That's probably a bit different from most robotic applications where they would be used in isolation. I can certainly understand cascading failures when nearby units have to take up additional load.

This is exactly the mechanism that I have been looking for, but is much bigger than what I would like to play with... build a tube an inch or less in diameter, and be able to run via PWM commands from a hobby RC transmitter and you have something I would buy and use in all sorts of robots.

The earlier non-locking versions had a flat coil without any holes. The "slinky" part had a groove along the top and bottom surfaces. When the actuator was fed out, each flat coil would sit in the groove on top of the slinky. If the actuator were not in constant compression, the entire assembly would fall apart.

I currently have two bout 22" electric actuators on the tilt front end of my 1984 Chevy Silverado P/U. I don't have the room, with the front end closed, for anything longer than the 22", but I need something that can throw open the front end a bit further. I would need maybe another foot and may not need to go the whole foot. I'd appreciate any suggestions and an idea of what the cost would be. Thank you

Would love to see this technology in the marine industry. Use this inside of a telescoping pedestal. Outside shiny cover that looks nice with this inside that allows tables to go all the way down to the floor without taking up to much below deck space.